on trains

So much for frostbite. When we arrived in Middlebury the car thermometer read 49-degrees. It's back to normal today, somewhere in the 30s. We took a stroll downtown this afternoon and stopped to look at the train because it seems that every kid thinks trains are exciting. Thad noticed that this train had a warning on the back of it, which baffled us both. Is train humping a big problem? Really?